Modular offshore structure system

ABSTRACT

A modular-like system of offshore structures for imparting flexibility to the offshore exploration and production and transportation industries so that exploration, production and development work can take place over a large range of marine depths and operational circumstances with one or more marine vessels.

United States Patent 1191 1111 3,874,180 Sumner 5] Apr. 1, 1975 [54]MODULAR OFFSHORE STRUCTURE 2,913,880 11/1959 1266111111 et a1. 61/46.5SYSTEM 2,941,370 6/1960 Walker 61/46.5 2,967,400 1/1961 Grant et. a1....61/465 Inventor: Maurice Sumner, 1718 Lubbock 3,385,464 5/1968 Courbon61/46 St, Houston, TEX. 77007 3,390,531 7/1968 Johnston et a1 61/46.5 X3,429,133 2/1969 Hauber 61/46.5 [22] 1972 3,466,878 9/1969 Esquillan eta1. 6l/46.5 2 A 1 N 243 790 3,593,529 7/1971 Smulders 61/46.5 1 PP R 9 SD 3,645,104 2 1972 Hogan 61/46.5

elated U. Application ata [60] Division of Ser. No. 107,288, Jan. 18,1971, Pat. No. FOREIGN PATENTS OR APPLICATIONS 3,716,993, which is acontinuation-inart of S N 188,414 3/1967 U.S.S.R.. 6l/46.5 649,889, June29, 1967, Pat. No. 3,575,005.

Primary ExaminerJacob Shapiro [52] US. Cl 61/46.5, 61/50, 114/.5 D,Attorney, Agent, or Firm-Kenneth H. Johnson 114/435 [51] It ll. C1.E021) 17/04, EOZC 5/00 [57 ABSTRACT [58] Fleld of Search 61/46.5, 46,65, 67;

114/5 D 435; 9/8; 52/224, 648, 653; 175/7 A modular-hke system ofoffshore structures for 1m- 8 9 partlng flexibility to the offshoreexploration and production and transportation industries so thatexplora- [56] References Cited tion, production and development work cantake place over a large range of marine depths and opera- UNITED STATESPATENTS tional circumstances with one or more marine vessels. 2,592,4484/1952 MCMCnimfZn 61/46.5 0 2,908,141 10/1959 Marsh, Jr 61/46.5 X 20Claims, 102 aw g Flgures PATENTEDAPR' 1197s 3.874.180

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MODULAR OFFSHORE STRUCTURE SYSTEM CROSS REFERENCES This application is adivision of my earlier application, Ser. No. lO7,288,filed Jan. 18,1971U.S. Pat. No. 3,716,993, which is a continuation-in-part of my earlierapplication Ser. No. 649,889, filed June 29, 1967, now US. Pat. No.3,575,005.

BACKGROUND OF THE INVENTION There is in the offshore drilling,production, and transportation industry a variety of structures forsupporting men and machinery at stations offshore. The structures aresimilar in basic function, namely to support the men and machinery inaccomplishing their assigned functions. Otherwise the structures aresignificantly different in that some are mobile while others arestationary; and some are founded on the marine floor while others float.The mobile structures are commonly called mobile rigs while the fixedones are fixed platforms. These rigs and platforms are generallyclassified as either drill ships, semi-submersibles, submersibles,jackups, pile jackets, or one of a few other hybrid designs. Each ispeculiarly designed and adapted for a fairly limited set of operationalcondi tions. As a result, there is restrictive flexibility of use. Forexample, the fixed frame design, commonly known as the aforementionedpile jacket, is best suited for permanent stations in water of a fewhundred feet or less. All other current types are mobile and moreexpensive as a result, and therefore they are well suited forexploration work, but not so well suited for long duration stationaryproduction work. However, even production work is not truly permanentand reusability would be a significant consideration in the design ofarig for pro duction purposes. Fixed platforms are seldom used inexploration work because the cost of building a new platform for eachexploratory hole is almost prohibi tive, except in shallow, protectedwaters. Thus fixed platforms are primarily production type structures.

In contrast to the permanent station characterizing the fixed framedesign, the most mobile type of offshore platform is the drill ship withits appropriate stabilizing and stationing apparatus such as thrusters,anchors, and winches. The ship certainly is not best suited forpermanent stationing because it is particularly sensitive to wave actionby reason of the wide surface area of structure exposed to the water,and the use of thrusters to maintain stationing for long periods oftime, as would be necessary for production activities, is economicallyunfeasible because of fuel consumption and the necessarily continuoushuman monitoring which is required. Also, of course, the ship isvulnerable to storms and generally adverse conditions.

Intermediate the permanent station characterizing the fixed frame andthe high mobility of the drill ship are the family of rigs known asjackups. The jackup rig has some of the advantages of both the fixedframe and the drill ship. It is analogous to the former in that it issupported on the marine floor, and therefore is quite stable andrequires no continuous operation or monitoring to maintain position.And, when the legs are raised, it can be towed from place to place so asto thereby provide a degree of mobility analogous to the drill ship. Thelegs can, of course, be lowered to varying elevations so as to providethe jackup with an adaptability to a variety of depths.

The aforementioned submersibles are also an intermediate form of rig.The submersibles and also the semi-submersibles have good stability,each is suited to its depth, the semi-submersible to deep water, thesubmersible bottom-founded frame to shallow water. Both are more stablebut less mobile than the drill ship. They cannot be moved in heavyweather without jeopardy to themselves, their crew, and the towingvessel; and indeed some have even been lost while being moved in calmwaters.

It thus becomes evident without further elaboration that each of thevarious types of offshore drilling rigs commonly used is well suitedonly to a relatively narrow range of operation. As a result, a companyor firm which chooses to operate offshore must elect the particular typeof rig best suited for its contemplated initial endeavor and thereafterbe committed to the limitations of that rig when it is used insubsequent drilling operatlons.

The limitations inherent in the state of the art are best illustrated bya brief examination of one of the more common types of mobile rig. Thejackup rig, as previously noted, has certain of the advantageouscharacteristics of the pile jacket in that it is founded on the bottomin a stable way while the apparatus it carries is supported clear of thehighest anticipated waves so that the whole is a fairly stablesemi-permanent, albeit expensive, station. Mobility is achieved bylowering its bouyant platform to the water, and raising the legs fromthe marine floor, so that the whole can then be floatably moved toanother location. Although jackup rigs in general are adapted to arelatively wide range of operating depths, namely about 20 to perhaps500 feet, any single jackup is adapted, as a practical matter, to a verylimited subrange within this range. For example, if ajackup of the priorart were to be designed for work in the Gulf of Mexico in water of 200foot depth, it certainly could not work in depths of 400 feet becauseits legs would not reach the bottom. Likewise, it could not workcompetitively, that is economically, in water depths of say 60 feetbecause other less expensive jackup rigs would be available for thatwork. So, although in a physical sense jackup rigs can work in a widerange of depths, they cannot in an individual and in an economic senseencompass a very large range of usefulness.

Therefore, it might be concluded from the above brief discussion thatthe offshore operator is restricted to a fixed location rig whichrepresents a substantial investment, or to a mobile rig which representsa very substantial investment but which is adapted only to a relativelynarrow range of operational depths which may represent a certain classof locations.

SUMMARY OF THE INVENTION The present invention endeavors to broaden theflexibility in use for offshore rnobile rigs and ancillary structures,and to allow a wider variety of choices than presently exist. This isaccomplished not be a specific modification to a particular type ofexisting rig, but by presenting the concept of an entire new family ofmodular elements which are adapted to cooperate with one another inorder to provide a plurality of alternative structures which enable theuser to operate an offshore drilling platform in a much broader range ofdepts and

1. An offshore marine structure founded on a marine floor comprising: aplatform at or above the surface of the water; a footing memberextending below the surface of the water to a point above andnoncontiguous to the marine floor; and containing a plurality of meansfor guiding and holding pilings in a pile cluster in downwardlydivergent bipodal array; a piling, said piling being driven into themarine floor and; means rigidly connecting said platform and saidfooting member.
 2. The offshore marine structure according to claim 1wherein said array of bipods is peripheral.
 3. The offshore marinestructure according to claim 2 wherein said array of bipods is circular.4. The offshore marine structure according to claim 3 wherein said arrayof downwardly divergent bipods lies on the rulings of an inner cone andan outer cone.
 5. An offshore marine structure founded on a marine floorcomprising: platform at or above the surface of the water; a footingmember extending below the surface of the water to a point above andnoncontiguous to the marine floor; and containing a plurality of meansfor guiding and holding piling in a pile cluster in downwardly divergenttripodal array; a piling, said piling being driven into the marine floorand; means rigidly connecting said platform and said footing member. 6.An offshore marine structure founded on a marine floor comprising:platform at or above the surface of the water; a footing memberextending below the surface of the water to a point above andnoncontiguous to the marine floor; and containing a plurality of meansfor guiding and holding piling in a pile cluster in downwardly divergentarray, wherein said array is as the rulings on a hyperboloid ofrevolution of one sheet; a piling, said piling being driven into themarine floor and; means rigidly connecting said platform and saidfooting member.
 7. An offshore marine structure comprising: a platformfounded below the surface of the water having a vertical axis; a vesselsharing said vertical axis of said founded platform; means releasableconnecting said founded platform and said vessel for founding saidvessel on said platform for operations from said vessel; means forchanging the elevation of said vessel when releasable connected to saidfounded platform; means for floatational rotation of said vessel aboutsaid axis so as to change the relative horizontal location of saidvessel to said founded platform.
 8. The offshore structure according toclaim 7 wherein said founded platform is circular in horizontal crosssection.
 9. The offshore structure according to claim 8 wherein saidfounded platform is toroidal.
 10. The offshore structure according toclaim 7 wherein said means for releasably connecting said foundedplatform and said vessel comprises legs and said means for changing theelevation of said vessel comprises a jacking means.
 11. The process ofchanging the relative horizontal location of a vessel elevated above thewater on an offshore marine structure comprising a founded platformhaving a vertical axis, said vessel sharing said vertical axis of saidfounded platform, means releasable connecting said platform and saidvessel, means for changing the elevation of said vessel when releasablyconnected to said founded platform comprising the steps of: loweringsaid vessel to a floating position on the water; releasing said meansconnecting said founded platform and said vessel; rotating said vesselabout said axis to a different horizontal position, releasableconnecting said founded platform and said vessel, and; elevating saidvessel above the surface of the water.
 12. An offshore marine structurecomprising at least two consecutive vertical groupings of bipods, eachsuccessively higher grouping after the first being supported by theimmediately succeeding grouping thereto, said groupings of bipods beingformed by at least three members corresponding to three equally spacedclockwise rulings in downward progression on a hyperboloid of revolutionof one sheet and at least three opposing members corresponding to threecounterclockwise rulings in downward progression on a hyperboloid ofrevolution of one sheet.
 13. The offshore marine structure according toclaim 12 comprising four equally spaced members in clockwise relationand four opposed members in counterclockwise relation.
 14. The offshoremarine structure according to claim 12 comprising a plurality ofclockwise and counterclockwise members.
 15. The offshore marinestructure according to claim 14 comprising sufficient members in theouter perimeter thereof to define a hyperboloid of revolution of onesheet.
 16. The offshore marine structure according to claim 12 whereinsaid bipods are pilings driven into the marine floor.
 17. The offshoremarine structure according to claim 16 wherein said bipods support atoroidal ring.
 18. An offshore marine structure comprising: a foundedplatform extending above the surface of the water; a vessel, releasablyconnected to said platform; two legs movable connected with said vesseland spaced from and outboard of said vessel; and means of moving saidvessel vertically on only said two legs, said vessel being elevatedabove the surface of the water on said legs, said legs being on oppositeends of a horizontal axis of said vessel.
 19. The offshore marinestructure according to claim 18 wherein the legs are at opposite ends ofthe longer axis of the vessel.
 20. The offshore marine structureaccording to claim 18 wherein the legs are at opposite ends of theshorter axis of the vessel.